1. Field of the Invention
The present invention relates to a method of manufacturing a head unit having an ink-jet head which ejects ink to a recording medium.
2. Description of Related Art
Japanese Unexamined Patent Publication No. 2005-186383 discloses an ink-jet head assembly including a plurality of ink-jet heads each having an elongated plate with both ends thereof not being in contact with other plates, and a frame to which each of the ink-jet heads is fixed via the elongated plate. Each of the ink-jet heads includes a head main body, a reservoir unit, and the elongated plate. The head main body has a passage unit and an actuator unit. The reservoir unit is fixed to an upper face of the passage unit. The elongated plate is fixed to an upper face of the reservoir unit. The passage unit is formed therein with a plurality of individual ink passages each extending from a manifold channel through a pressure chamber to a nozzle. The actuator unit applies pressure to ink in the pressure chamber.
In the ink-jet head assembly, a plurality of through holes are formed in the elongated plate of the ink-jet head. The through holes are formed through a thickness of the plate, and arranged along a lengthwise direction of the plate. On the upper face of the reservoir unit, threaded holes are formed at positions corresponding to the through holes. Bolts which are inserted through the respective through holes are screwed into the threaded holes, so that the elongated plate and the reservoir unit are fixed to each other while a flat lower face of the elongated plate is being in tight contact with the upper face of the reservoir unit. As a result, upper and lower faces of the reservoir unit are prevented from being bent in a direction perpendicular to a plane direction, and therefore upper and lower faces of the passage unit are corrected into parallel with the lower face of the elongated plate. This improves flatness of the lower face of the passage unit, that is, flatness of an ink ejection face in which a plurality of nozzles open.